Glow discharge in a reduced atmosphere of air has long been the accepted method to render carbon support films for electron microscopy (EM) hydrophilic (i.e. with a net negative charge) prior to adsorbing suspensions of biological material to them [c.f. Dubochet et al, J. Ultrastruct. Res. 35, 147-167, 1971]. This is commonly performed in a vacuum evaporator by placing the EM grid between two parallel electrode plates to which a high voltage is applied to cause a glow discharge.
While the prior techniques for rendering carbon support films or the like hydrophilic give useful results, there is still considerable room for improvement. For example, it would be desirable if glow discharge apparatus used to impart hydrophilicity could be made more convenient, faster and less expensive. This is the purpose of the present invention.